US9674619B2 - MEMS microphone and forming method therefor - Google Patents

MEMS microphone and forming method therefor Download PDF

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US9674619B2
US9674619B2 US14/004,822 US201214004822A US9674619B2 US 9674619 B2 US9674619 B2 US 9674619B2 US 201214004822 A US201214004822 A US 201214004822A US 9674619 B2 US9674619 B2 US 9674619B2
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mems microphone
substrate
bonding
forming
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US20140003633A1 (en
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Lianjun Liu
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MEMSEN ELECTRONICS Inc
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MEMSEN ELECTRONICS Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
    • H04R1/04—Structural association of microphone with electric circuitry therefor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48135—Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip
    • H01L2224/48137—Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip the bodies being arranged next to each other, e.g. on a common substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/00014—Technical content checked by a classifier the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/003—Mems transducers or their use
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/02—Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups
    • H04R2201/029—Manufacturing aspects of enclosures transducers

Definitions

  • the present invention relates to the field of micro-electro-mechanical system process, and particularly to a Micro-Electro-Mechanical Systems (MEMS) microphone and a forming method therefore.
  • MEMS Micro-Electro-Mechanical Systems
  • MEMS Micro-Electro-Mechanical System
  • ECM Electret Condenser Microphone
  • the MEMS microphone is a miniature microphone made by etching a pressure sensing diaphragm on a semiconductor using micro-electro-mechanical system process, and is widely used in mobile phone, headset, notebook computer, video camera and car.
  • CMOS Complementary Metal Oxide Semiconductor
  • package structure for MEMS microphone has attracted many development activities in recent years. Many companies invest a lot of money and scientific manpower to study the package structure for MEMS microphone.
  • CMOS circuit and MEMS microphone are manufactured separately, then the CMOS circuit and MEMS microphone are attached on a substrate, and finally, the CMOS circuit is coupled to the MEMS microphone by wire-bonding technology.
  • the package structure includes a package substrate 100 , which has an opening in communication with the package substrate 100 , with the opening being adapted to pass through an acoustic signal; a MEMS microphone 110 and a CMOS circuit 120 adapted to control the MEMS microphone 110 which are located respectively on the package substrate 100 ; a wire 140 electrically coupling the MEMS microphone 110 to the CMOS circuit 120 ; and a package frame 130 by which the package substrate 100 , the MEMS microphone 110 and the CMOS circuit 120 are covered.
  • the CMOS circuit 120 and the MEMS microphone 110 are manufactured separately, and then are packaged on the package substrate 100 by the wire-bonding technology.
  • the package structure for the MEMS microphone packaged on the package substrate 100 by wire-bonding technology has a large size, and needs an additional package frame 130 , which has a complex manufacturing and packaging process, a large size, and high cost.
  • a problem to be solved in an embodiment of the present invention is to provide a MEMS microphone and a forming method therefore, which have a simple manufacturing and packaging process, a small size, good signal-to-noise ratio performance, and high interference immunity.
  • a MEMS microphone is provided according to an embodiment of the present invention, and the MEMS microphone includes:
  • a first base-structure having a first bonding surface and including a MEMS microphone component and a first conductive bonding structure having the first bonding surface
  • a second base-structure having a second bonding surface and including a circuit and a second conductive bonding structure, with the second conductive bonding structure having the second bonding surface;
  • first base-structure is bonded correspondingly to the second base-structure via the first conductive bonding structure and the second conductive bonding structure.
  • the MEMS microphone component may include a sensitive diaphragm and a fixed electrode corresponding to the sensitive diaphragm.
  • the MEMS microphone may further include: a first structure located in the first base-structure, wherein the first structure is a first opening or a first air cavity.
  • the sensitive diaphragm or the fixed electrode may be exposed through the first opening.
  • the MEMS microphone may further include: a second structure located in the second base-structure, wherein the second structure is a second opening or a second air cavity.
  • the sensitive diaphragm or the fixed electrode may be exposed through the second opening.
  • the first structure may be in communication with the second structure.
  • the first conductive bonding structure may include a first top-layer electrode and a bonding layer located on a surface of the first top-layer electrode.
  • the first top-layer electrode is located in the same layer as the fixed electrode or the sensitive diaphragm, and is made from the same material as the fixed electrode or the sensitive diaphragm.
  • the MEMS microphone may further include: a bonding pad located on the first bonding surface and a third opening through which the bonding pad located on the first bonding surface is exposed.
  • the MEMS microphone may further include: a bonding pad located on the second bonding surface and a fourth opening through which the bonding pad located on the second bonding surface is exposed.
  • the MEMS microphone component may further include a travel stopper which is adapted to prevent stiction between the sensitive diaphragm and the fixed electrode.
  • the sensitive diaphragm may be made from polycrystalline silicon material.
  • a method for forming a MEMS microphone is further provided according to the embodiment of the present invention, and the method includes:
  • first base-structure which has a first bonding surface and includes a MEMS microphone component and a first conductive bonding structure having the first bonding surface;
  • a second base-structure which has a second bonding surface and includes a circuit and a second conductive bonding structure having the second bonding surface
  • the MEMS microphone component may include a sensitive diaphragm and a fixed electrode corresponding to the sensitive diaphragm.
  • the method for forming the MEMS microphone may further include:
  • first structure located in the first base-structure, wherein the first structure is a first opening or a first air cavity.
  • the method for forming the MEMS microphone may further include: forming a second structure located in the second base-structure, wherein the second structure is a second opening or a second air cavity.
  • the method for forming the MEMS microphone may further include: communicating the first structure with the second structure.
  • the method for forming the MEMS microphone may further include: forming a bonding pad on the first bonding surface of the first base-structure; and forming a third opening through which the bonding pad located on the first bonding surface is exposed.
  • the method for forming the MEMS microphone may further include: forming a bonding pad on the second bonding surface of the second base-structure; and forming a fourth opening through which the bonding pad located on the second bonding surface is exposed.
  • the first conductive bonding structure may include a first top-layer electrode and a bonding layer located on a surface of the first top-layer electrode.
  • the MEMS microphone component may include a sensitive diaphragm and a fixed electrode corresponding to the sensitive diaphragm, and the first top-layer electrode is formed in the same process step as the fixed electrode or the sensitive diaphragm.
  • the embodiment of the present invention has the following advantages as compared with the prior art.
  • the first base-structure is bonded to the second base-structure via the first conductive bonding structure and the second conductive bonding structure, specifically, the second base-structure within which a circuit is formed is bonded correspondingly to the first base-structure within which a MEMS microphone is formed via the first conductive bonding structure and the second conductive bonding structure.
  • the MEMS microphone formed in the embodiment of the present invention has a small size and high performance.
  • the MEMS microphone and the forming method therefore according to the embodiment of the present invention has a simple manufacturing and packaging process, a small size, good signal-to-noise ratio performance, and high interference immunity.
  • FIG. 1 is a schematic diagram of a package structure for a MEMS microphone in the prior art
  • FIG. 2 is a schematic flowchart of a method for forming a MEMS microphone according to an embodiment of the present invention
  • FIG. 3 is a schematic flowchart of a method for forming a MEMS microphone according to a first embodiment of the present invention
  • FIG. 4 is a schematic flowchart of a method for forming a MEMS microphone according to a second embodiment of the present invention
  • FIG. 5 to FIG. 16 are process diagrams of a method for forming the MEMS microphone according to the second embodiment of the present invention.
  • FIG. 17 is a schematic flowchart of a method for forming a MEMS microphone according to a third embodiment of the present invention.
  • FIG. 18 is a schematic flowchart of a method for forming a MEMS microphone according to a fourth embodiment of the present invention.
  • FIG. 19 is a schematic flowchart of a method for forming a MEMS microphone according to a fifth embodiment of the present invention.
  • FIG. 20 to FIG. 22 are process diagrams of a method for forming the MEMS microphone according to the fifth embodiment of the present invention.
  • FIG. 23 is a schematic flowchart of a method for forming a MEMS microphone according to a sixth embodiment of the present invention.
  • FIG. 24 to FIG. 27 are process diagrams of a method for forming the MEMS microphone according to the sixth embodiment of the present invention.
  • FIG. 28 is a schematic diagram of a MEMS microphone according to a seventh embodiment of the present invention.
  • FIG. 29 is a schematic diagram of a MEMS microphone according to an eighth embodiment of the present invention.
  • the existing MEMS microphone is formed in such a method that a CMOS circuit and a MEMS microphone are manufactured separately and then are packaged on a package substrate by wire-bonding technology, which has a complex manufacturing and packaging process, a large size, and high cost.
  • a preferred method for forming a MEMS microphone is proposed by the inventor of the present invention, referring to FIG. 2 , and the method includes the following steps S 11 to S 13 .
  • Step S 11 providing a first base-structure, which has a first bonding surface and includes a MEMS microphone component and a first conductive bonding structure, with the first conductive bonding structure having the first bonding surface.
  • Step S 12 providing a second base-structure, which has a second bonding surface and includes a circuit and a second conductive bonding structure, with the second conductive bonding structure having the second bonding surface.
  • Step S 13 bonding correspondingly the first base-structure to the second base-structure via the first conductive bonding structure and the second conductive bonding structure.
  • a MEMS microphone formed by the forming method described above includes:
  • a first base-structure having a first bonding surface and including a MEMS microphone component and a first conductive bonding structure having the first bonding surface
  • a second base-structure having a second bonding surface and including a circuit and a second conductive bonding structure having the second bonding surface
  • first base-structure is bonded correspondingly to the second base-structure via the first conductive bonding structure and the second conductive bonding structure.
  • the MEMS microphone component includes a sensitive diaphragm and a fixed electrode corresponding to the sensitive diaphragm, and further includes a travel stopper which is adapted to prevent the stiction between the sensitive diaphragm and the fixed electrode.
  • the MEMS microphone component in the present invention is not limited to the MEMS microphone component exemplified in this embodiment.
  • the existing MEMS microphone components, such as a microphone having a sensitive diaphragm and a fixed electrode corresponding to the sensitive diaphragm, and a microphone having a travel stopper will all fall within the scope of protection of the technical solution of the present invention.
  • the MEMS microphone described above further includes: a first structure located in the first base-structure, wherein the first structure includes a first opening or a first air cavity.
  • the sensitive diaphragm or the fixed electrode is exposed through the first opening.
  • the MEMS microphone further includes: a second structure located in the second base-structure, wherein the second structure includes a second opening or a second air cavity.
  • the sensitive diaphragm or the fixed electrode is exposed through the second opening.
  • a preferred method for forming a MEMS microphone is proposed by the inventor of the present invention, referring to FIG. 3 , and the method includes the following steps S 101 to S 106 .
  • Step S 101 providing a first substrate having a first surface and a second surface opposite to the first surface; forming a sensitive diaphragm and a dielectric layer by which the sensitive diaphragm is covered being formed on the first surface of the first substrate; forming a first top-layer electrode and a fixed electrode which is corresponding to the sensitive diaphragm on a surface of the dielectric layer, and forming the fixed electrode having a plurality of through holes running through the fixed electrode.
  • Step S 102 providing a second substrate within which a circuit is formed, with the second substrate having a third surface and a fourth surface, and forming a second top-layer electrode, corresponding to the first top-layer electrode, on the third surface of the second substrate.
  • Step S 103 bonding the top-layer electrode to the second-layer electrode.
  • Step S 104 removing a part of the first substrate from the second surface to form a first opening.
  • Step S 105 removing a part of the second substrate to form a second opening.
  • Step S 106 removing the dielectric layer corresponding to the sensitive diaphragm, so that a variable capacitor is formed between the sensitive diaphragm and the fixed electrode, and the capacitance of the variable capacitor changes under the stimulus of an acoustic signal.
  • the first opening may be further communicated with the second opening to form an air cavity.
  • the first opening may be not communicated with the second opening. Whether or not the first opening is communicated with the second opening in the MEMS microphone according to this embodiment can be selected by those skilled in the art depending on the actual need. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • the method for forming the MEMS microphone according to the first embodiment further includes a step of forming a travel stopper which is adapted to prevent stiction between the sensitive diaphragm and the fixed electrode.
  • the first top-layer electrode may be a single layer structure or a multilayer stack structure
  • the second top-layer electrode may be a single layer structure or a multilayer stack structure
  • the first top-layer electrode may be a conductor, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the second top-layer electrode may be a conductor, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the first base-structure within which a MEMS microphone is formed is bonded correspondingly to the second base-structure having a circuit via the first top-layer electrode and the second top-layer electrode, specifically via eutectic bonding of the first top-layer electrode made from a metal or an alloy and the second top-layer electrode made from a metal or an alloy.
  • the first base-structure includes the first substrate and the sensitive diaphragm and the fixed electrode formed on the first substrate.
  • the second base-structure includes the second substrate having a circuit and the second top-layer electrode.
  • the first top-layer electrode is a first conductive bonding structure
  • the second top-layer electrode is a second conductive bonding structure.
  • the first top-layer electrode includes a polycrystalline silicon electrode layer formed on the surface of the dielectric layer and an adhesion layer located on a surface of the polycrystalline silicon electrode layer.
  • the adhesion layer is a conductor, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the second top-layer electrode is a single layer structure or a multilayer stack structure, and the second top-layer electrode is made from a conductive material.
  • the second substrate having the circuit is bonded correspondingly to the first substrate within which the MEMS microphone is formed via the adhesion layer of the first top-layer electrode.
  • the first top-layer electrode may be a single layer structure or a multilayer stack structure, and the first top-layer electrode is made from a conductive material.
  • the second top-layer electrode includes an electrode layer formed on the third surface of the second substrate and an adhesion layer located on a surface of the electrode layer.
  • the second substrate having the circuit is bonded correspondingly to the first substrate within which the MEMS microphone is formed via the adhesion layer of the second top-layer electrode.
  • the first base-structure is bonded to the second base-structure via the first top-layer electrode and the second top-layer electrode.
  • the second base-structure having the circuit is bonded correspondingly to the first base-structure having the MEMS microphone via the first top-layer electrode and the second top-layer electrode, and the first top-layer electrode corresponds to the second top-layer electrode.
  • the MEMS microphone formed in the embodiment of the present invention has a small size and high performance.
  • the MEMS microphone and the forming method therefore according to the embodiment of the present invention has a simple manufacturing and packaging process, a small size, good signal-to-noise ratio performance, and high interference immunity.
  • a MEMS microphone formed by the method for forming a MEMS microphone described above includes: a first substrate; a dielectric layer located on a surface of the first substrate; a first top-layer electrode located on a surface of the dielectric layer; a second top-layer electrode located on a surface of the first top-layer electrode; a second top-layer electrode; a second substrate which has a circuit formed within; an air cavity running through the first substrate and located within the second substrate; a sensitive diaphragm located within the air cavity; and a fixed electrode located within the air cavity and corresponding to the sensitive diaphragm; with a plurality of through holes running through the fixed electrode are formed.
  • the first top-layer electrode is a single layer structure or a multilayer stack structure.
  • the first top-layer electrode is made from a conductor material, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the first top-layer electrode is a multilayer stack structure
  • the first top-layer electrode includes a polycrystalline silicon electrode layer formed on the surface of the dielectric layer and an adhesion layer located on a surface of the polycrystalline silicon electrode layer.
  • the second top-layer electrode is a single layer structure or a multilayer stack structure.
  • the second top-layer electrode is made from a conductor material, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the second top-layer electrode includes an electrode layer formed on the third surface of the second substrate and an adhesion layer located on a surface of the electrode layer.
  • the MEMS microphone further includes a plurality of interconnects, which are located on the first substrate and located in the same layer as the sensitive diaphragm.
  • the MEMS microphone further includes a conductive plug located within the dielectric layer and electrically coupled to the interconnect.
  • the conductive plug is made from the same material as the fixed electrode, which is polycrystalline silicon.
  • the polycrystalline silicon electrode layer of the first top-layer electrode is located in the same layer as the fixed electrode, and is made from the same material as the fixed electrode.
  • the MEMS microphone according to the embodiment of the present invention has a small size, high performance, good signal-to-noise ratio performance, and high interference immunity.
  • FIG. 4 is a schematic flowchart of a method for forming a MEMS microphone according to a second embodiment of the present invention, and the method includes the following steps S 201 to S 212 .
  • Step S 201 providing a first substrate having a first surface and a second surface opposite to the first surface.
  • Step S 202 forming, on the first surface of the first substrate, a sensitive diaphragm and a plurality of interconnects.
  • Step S 203 forming a dielectric layer by which the sensitive diaphragm and the plurality of interconnects are covered.
  • Step S 204 forming a plurality of first through holes within the dielectric layer, with the first through holes being corresponding to the interconnect.
  • Step S 205 forming a polycrystalline silicon layer on a surface of the dielectric layer, with the polycrystalline silicon layer filling the first through hole.
  • Step S 206 etching the polycrystalline silicon layer to form a fixed electrode corresponding to the sensitive diaphragm and a top-layer electrode corresponding to the first through hole, with the fixed electrode having a second through hole running through the fixed electrode.
  • Step S 207 forming a bonding layer on a surface of the top-layer electrode to form a first top-layer electrode.
  • Step S 208 providing a second substrate within which a circuit is formed, with the second substrate having a third surface and a fourth surface, a second top-layer electrode being formed on the third surface of the second substrate, and the second top-layer electrode being corresponding to the first top-layer electrode.
  • Step S 209 aligning the second top-layer electrode with the first top-layer electrode, and bonding the second top-layer electrode to the first top-layer electrode via the bonding layer.
  • Step S 210 removing a part of the first substrate from the second surface to form a first opening.
  • Step S 211 removing a part of the second substrate from the fourth surface to form a second opening.
  • Step S 212 removing the dielectric layer corresponding to the first opening from the first opening and/or the second opening, until the first opening becomes in communication with the second opening, so as to form an air cavity.
  • FIG. 5 to FIG. 16 are process diagrams of a method for forming the MEMS microphone according to the second embodiment of the present invention.
  • a first substrate 200 is provided.
  • the first substrate 200 has a first surface I and a second surface II opposite to the first surface I.
  • the first substrate 200 may be made from a semiconductor material.
  • the first substrate 200 may be made from a single crystal semiconductor material such as single crystal silicon or single crystal silicon-germanium (e.g., a group II-VI compound semiconductor and a group III-V compound semiconductor).
  • the first substrate 200 may also be an amorphous substrate and a polycrystalline.
  • the first substrate 200 is a single crystal silicon substrate 202 having an upper surface on which an insulating layer 201 is formed.
  • the first surface I of the first substrate 200 is the upper surface of the insulating layer 201
  • the second surface II of the second substrate 200 is a lower surface of the single crystal silicon substrate 202 .
  • the insulating layer 201 is adapted to isolate a sensitive diaphragm from a plurality of interconnects formed in the subsequent step.
  • the insulating layer 201 may be made from silicon oxide, silicon nitride or silicon oxynitride.
  • the process for forming the insulating layer 201 is a deposition process or a thermal oxidation process.
  • the insulating layer 201 may be made from silicon oxide material, and the insulating layer 201 is formed by performing oxidation on the first surface of the single crystal silicon substrate 202 by a thermal oxidation process.
  • the thickness and the material of the insulating layer 201 can be selected by those skilled in the art depending on the MEMS microphone to be formed. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • a sensitive diaphragm 210 and a plurality of interconnects 211 are formed on the first surface I of the first substrate 200 .
  • the sensitive diaphragm 210 is adapted to form a capacitor with a fixed electrode to be formed later.
  • the sensitive diaphragm 210 may vibrate under the stimulus of an acoustic signal to convert the acoustic signal into an electrical signal.
  • the sensitive diaphragm 210 is made from low stress polycrystalline silicon material, and the shape of the sensitive diaphragm 210 may be square, circular or other shapes.
  • a suitable shape of the sensitive diaphragm 210 can be selected by those skilled in the art depending on the MEMS microphone to be formed. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • the sensitive diaphragm 210 is made from low stress polycrystalline silicon material, so that the size and the production cost of the MEMS microphone using the sensitive diaphragm 210 can be further reduced.
  • the interconnect 211 is adapted to electrically couple the sensitive diaphragm 210 of the MEMS microphone.
  • the interconnect 211 is made from a conductive material.
  • the position where the interconnect 211 is formed, the number and the shape of the interconnect 211 may be determined depending on the specific MEMS microphone and can be selected by those skilled in the art depending on the MEMS microphone to be formed. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • the interconnect 211 may be made from the same material as that of the sensitive diaphragm 210 , which is low stress polycrystalline silicon.
  • the interconnect 211 may be formed in the same deposition process and the same etching process as the sensitive diaphragm 210 , so as to eliminate some process steps.
  • the specific step of forming the interconnect 211 and the sensitive diaphragm 210 includes: depositing a low stress polycrystalline silicon thin film (not shown) on the first surface I of the first substrate 200 by a chemical vapor deposition process; forming a photoresist layer (not shown) on a surface of the low stress polycrystalline silicon thin film; exposing and developing the photoresist layer using a mask corresponding to the interconnect 211 and the sensitive diaphragm 210 so as to form a photoresist pattern; and removing the low stress polycrystalline silicon thin film by a plasma etching process by using the photoresist pattern as a mask, until the first substrate 200 is exposed, so as to form the interconnect 211 and the sensitive diaphragm 210 .
  • the interconnect and the sensitive diaphragm are formed by etching the same polycrystalline silicon thin film, thus the interconnect is located in the same layer as the sensitive diaphragm.
  • the material of the interconnect 211 is different from that of the sensitive diaphragm 210 , a forming method in which the interconnect 211 is formed firstly and then the sensitive diaphragm 210 is formed, or another forming method in which the sensitive diaphragm 210 is formed firstly and then the interconnect 211 is formed, may be adopted, which will not be described in detail here.
  • the low stress polycrystalline silicon thin film may be doped when or after the low stress polycrystalline silicon thin film is formed so as to reduce the resistance of the interconnect 211 and the sensitive diaphragm 210 , and the low stress polycrystalline silicon thin film may be annealed so as to reduce the stress on the sensitive diaphragm 210 .
  • An ion implantation process or an in situ deposition and doping process may be used as the doping process, and a rapid annealing or a tube furnace annealing may be used as the annealing process.
  • a dielectric layer 220 is formed, by which the sensitive diaphragm 210 and the plurality of interconnects 211 are covered.
  • the dielectric layer 220 is made from a material which has a selective etching characteristic with respect to the sensitive diaphragm 210 and the interconnect 211 .
  • the dielectric layer 220 is made from silicon oxide.
  • the dielectric layer 220 is adapted to form an air cavity within the dielectric layer in the subsequent step, that is, a portion of the dielectric layer 220 corresponding to the air cavity will serve as a sacrifice layer which will be removed in the subsequent step.
  • the remaining portion of the dielectric layer 220 is adapted to electrically isolate the interconnect 211 from a conductive electrode to be formed later.
  • the process for forming the dielectric layer 220 is a deposition process, and is preferably a chemical vapor deposition.
  • step S 204 by carrying out step S 204 , a plurality of first through holes 211 are formed within the dielectric layer 220 , with the first through holes 221 being corresponding to the interconnect 211 .
  • a conductive plug is formed after the first through hole 221 is filled with a conductive material.
  • the conductive plug is adapted to electrically couple the interconnect 211 to an electrode corresponding to the interconnect 211 and located in other layers.
  • the specific step of forming the first through hole 221 includes: forming a photoresist layer (not shown) on a surface of the dielectric layer 220 ; exposing and developing the photoresist layer using a mask corresponding to the through hole 221 so as to form a photoresist pattern; etching the dielectric layer 220 by using the photoresist pattern as a mask to form the first through hole 221 , wherein the etching process may be wet etching or dry etching; and removing the photoresist pattern after the first through hole 221 is formed, wherein the removing process may be an ashing process.
  • a polycrystalline silicon layer 230 is formed on a surface of the dielectric layer 220 , with the polycrystalline silicon layer 203 filling the first through hole 221 .
  • a conductive plug 223 is formed by filling the first through hole 221 .
  • the polycrystalline silicon layer 230 formed on the surface of the dielectric layer 220 is adapted to form a fixed electrode and a first top-layer electrode in the subsequent step. Thereby the conductive plug 223 can be formed in the same deposition process as the polycrystalline silicon layer 230 , so as to eliminate some process steps.
  • the conductive plug 223 is formed in the same deposition process as the polycrystalline silicon layer 230 . Thereby the conductive plug 223 is made from the same material as that of the first top-layer electrode and the fixed electrode to be formed later, which is polycrystalline silicon.
  • the first through hole 221 may also be filled with a conductive material, and then a conductive material layer is formed on the surface of the dielectric layer 220 .
  • a suitable process can be selected by those skilled in the art depending on the specific process requirement. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • step S 206 by carrying out step S 206 , the polycrystalline silicon layer 230 is etched to form a fixed electrode 232 corresponding to the sensitive diaphragm 210 and a top-layer electrode 234 corresponding to the first through hole 221 , with the fixed electrode 232 having a second through hole 233 running through the fixed electrode 232 .
  • the specific step of forming the fixed electrode 232 and top-layer electrode 234 includes: forming a photoresist layer on a surface of the polycrystalline silicon layer 230 ; exposing and developing the photoresist layer using a mask corresponding to the fixed electrode 232 and the top-layer electrode 234 so as to form a photoresist pattern; and etching the polycrystalline silicon layer 230 by using the photoresist pattern as a mask, so as to form the fixed electrode 232 and the top-layer electrode 234 , with a plurality of second through holes 233 running through the fixed electrode 232 being formed within the fixed electrode 232 , and the top-layer electrode 234 being electrically coupled to the conductive plug 223 ; and removing the photoresist pattern.
  • the top-layer electrode 234 and the fixed electrode 232 are formed by etching the same polycrystalline silicon layer 230 , and thereby the top-layer electrode 234 is located in the same layer as the fixed electrode 232 .
  • the fixed electrode 232 is adapted to form a capacitor with the sensitive diaphragm 210 formed previously, and convert the acoustic signal sensed by the capacitor into an electrical signal.
  • the second through hole 233 running through the fixed electrode 232 is formed in the fixed electrodes 232 .
  • the second through hole 233 is adapted to pass through an acoustic signal, so that the acoustic signal is able to pass through the fixed electrode 232 without being isolated, therefore the acoustic signal can be sensed by the sensitive diaphragm 210 .
  • a bonding layer 235 is formed on a surface of the top-layer electrode 234 to from a first top-layer electrode.
  • the bonding layer 235 is adapted to bond a first substrate 200 to a second substrate.
  • the bonding layer 235 is made from a conductive bonding material, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the bonding layer 235 is formed on the surface of the top-layer electrode 234 by electron beam evaporation, sputtering or plating process, depending on the material of the bonding layer 235 .
  • the bonding layer 235 and the top-layer electrode 234 constitute the first top-layer electrode in this embodiment.
  • a second substrate 300 within which a circuit or a wiring is formed, with the second substrate 300 having a third surface III and a fourth surface IV, a second top-layer electrode 301 being formed on the third surface III of the second substrate 300 , and the second top-layer electrode 301 being corresponding to the first top-layer electrode 234 .
  • the second substrate 300 may include a semiconductor material.
  • the second substrate 300 may include a single crystal semiconductor material such as single crystal silicon or single crystal silicon-germanium.
  • the circuit (not shown) formed within the second substrate 300 functions to drive provide a drive bias to the MEMS microphone and process a signal output by the MEMS microphone. That is, when the MEMS microphone receives an acoustic signal, the acoustic signal can be sensed by the sensitive diaphragm 210 and transmitted to the circuit via the interconnect electrically coupled to the sensitive diaphragm 210 or the fixed electrode 232 , and processed by the circuit.
  • the circuit may be a CMOS circuit.
  • the forming process for the circuit is a standard forming process for a CMOS circuit, which will not be described in detail here.
  • a suitable CMOS circuit can be selected by those skilled in the art depending on a design and parameter of the MEMS microphone. Practically, the circuit may also be other circuits which are formed within the second substrate 300 , drive the MEMS microphone, and process the signal output by the MEMS microphone. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • a second top-layer electrode 301 is formed on the third surface III of the second substrate 300 .
  • the second top-layer electrode 301 is coupled to the CMOS circuit via the conductive plug located within the second substrate 300 . It should also be noted that part of the second top-layer electrode 301 is corresponding to the first top-layer electrode, and is adapted to bond to the first top-layer electrode, so as to bond correspondingly the first substrate to the second substrate and form an electrical connection structure.
  • the forming process for the second top-layer electrode 301 may be an existing semiconductor process.
  • the specific step of forming the second top-layer electrode 301 include: forming a conductive material layer on the third surface III of the second substrate 300 ; and removing a redundant portion of the conductive material layer by lithography process.
  • step S 209 by carrying out step S 209 , the second top-layer electrode 301 is aligned with the first top-layer electrode, and the second top-layer electrode 301 is bonded to the first top-layer electrode via the bonding layer 235 .
  • the bonding layer 235 is made from a conductive bonding material. Taking the bonding layer 235 is made from gold-tin alloy as an example, the second top-layer electrode 301 is aligned with the first top-layer electrode, and an annealing process is carried out, so that the second top-layer electrode 301 is bonded to the first top-layer electrode.
  • the first top-layer electrode corresponds to the second top-layer electrode 301 .
  • the first substrate is bonded to the second substrate, and the CMOS circuit is electrically coupled to the MEMS microphone via the second top-layer electrode 301 and the first top-layer electrode, and no additional wire-bonding process is needed.
  • step S 210 by carrying out step S 210 , a part of the first substrate 200 is removed from the second surface II to form a first opening 240 .
  • the first opening 240 is adapted to be an acoustic signal transmission port of the MEMS microphone, via which an acoustic signal is passed through to the sensitive diaphragm 210 of the MEMS microphone.
  • the process for forming the first opening 240 is an etching process, and specifically may be wet etching or dry etching.
  • the depth of the removed portion of the first substrate 200 can be set by those skilled in the art depending on the specific process requirement.
  • the sensitive diaphragm 210 may be exposed through the first opening, that is, the first opening runs through the first substrate 200 .
  • the running through the substrate 200 of the first opening 210 has a simple process, and no additional step of removing the remaining first substrate 200 is needed later.
  • the insulating layer 201 is exposed by the first opening 240 formed in step S 210 , that is, the first opening 240 runs through the single crystal silicon substrate 202 .
  • the first opening 240 formed in this embodiment does not run through the first substrate 200 , and the insulating layer 201 remains.
  • the etching process for the first opening 240 is generally a fast etching process, and the etching rate is high, and if the sensitive diaphragm 210 is exposed when the etching is carried out, the sensitive diaphragm 210 tends to be damaged due to the excessively fast rate, thereby resulting in the lowered performance of the MEMS microphone.
  • the sensitive diaphragm 210 may be protected by the insulating layer 201 , so that the sensitive diaphragm 210 will not be damaged during the etching process.
  • the insulating layer 201 is removed in a subsequent etching step having a strong controllability on etching. Thereby both the efficiency of the process step and the process will be improved.
  • the specific step of forming the first opening includes: forming, on the second surface II, a photoresist pattern corresponding to the first opening 240 ; and etching the first substrate 200 by using the photoresist pattern as a mask, until the insulating layer 201 is exposed, so as to form the first opening 240 .
  • step S 210 by carrying out step S 210 , a part of the second substrate 300 is removed from the fourth surface IV to form a second opening 310 .
  • the second opening 310 is adapted to form an acoustic signal transmission passage.
  • the forming process for the second opening 310 is an etching process, and specifically may be wet etching or dry etching.
  • the specific step of forming the second opening 310 includes: forming, on the fourth surface IV, a photoresist pattern corresponding to the second opening 310 ; etching the second substrate 300 by using the photoresist pattern as a mask, until the fixed electrode 232 is exposed entirely, so as to form the second opening 310 .
  • step S 212 by carrying out step S 212 , the dielectric layer 220 corresponding to the first opening 240 is removed from the first opening 240 and/or the second opening 310 , until the first opening 240 becomes in communication with the second opening 310 , so as to form an air cavity 320 .
  • the insulating layer 201 by which the sensitive diaphragm 210 is protected may be removed while the dielectric layer 220 is removed.
  • the sensitive diaphragm 210 will not be damaged because this removing process has a higher selectivity.
  • the air cavity 320 is adapted to provide a space for the sensitive diaphragm 210 , so that the sensitive diaphragm 210 is able to vibrate within the air cavity 320 .
  • the MEMS microphone formed adopting the package structure of the MEMS microphone described above includes:
  • a first substrate 200 a plurality of interconnects 211 formed on the first surface I of the first substrate 200 ; a dielectric layer 220 by which the plurality of interconnects 211 are covered; a conductive plug 223 located within the dielectric layer 220 and electrically coupled to the interconnect 211 ; a first top-layer electrode 234 located on the surface of the dielectric layer 220 and electrically coupled to the conductive plug 223 ; a bonding layer 235 located on a surface of the first top-layer electrode 234 ; a second top-layer electrode 301 located on a surface of the bonding layer 235 and corresponding to the first top-layer electrode 234 ; a second substrate 300 within which a circuit is formed, located on a surface of the second top-layer electrode 301 ; an air cavity 320 running through the first substrate 200 and the second substrate 300 ; a sensitive diaphragm 210 located within the air cavity 320 and located in the same layer as the interconnect 211 ; and a fixed electrode 232 232
  • the first substrate 200 may include a semiconductor material.
  • the first substrate 200 may include a single crystal semiconductor material such as single crystal silicon or single crystal silicon-germanium.
  • the first substrate 200 may include an amorphous substrate and a polycrystalline, such as a glass substrate.
  • the sensitive diaphragm 210 is made from low stress polycrystalline silicon material.
  • the interconnect 211 is adapted to electrically couple the sensitive diaphragm 210 of the MEMS microphone.
  • the interconnect 211 is made from a conductive material.
  • the first top-layer electrode 234 , the conductive plug 223 , and the fixed electrode 232 are made from polycrystalline silicon material.
  • the second substrate 300 may include a semiconductor material.
  • the second substrate 300 may include a single crystal semiconductor material such as single crystal silicon or single crystal silicon-germanium.
  • a circuit or a wiring (not shown) is formed within the second substrate 300 .
  • the circuit functions to drive the MEMS microphone. That is, when the MEMS microphone receives an acoustic signal, the acoustic signal can be sensed by the sensitive diaphragm 210 and transmitted to the circuit via the interconnect electrically coupled to the sensitive diaphragm 210 or the fixed electrode 232 , and processed by the circuit.
  • the circuit may be a CMOS circuit.
  • the MEMS microphone formed in the second embodiment may further include a travel stopper (not shown) which is adapted to prevent the stiction between the sensitive diaphragm and the fixed electrode.
  • a travel stopper (not shown) which is adapted to prevent the stiction between the sensitive diaphragm and the fixed electrode.
  • the second substrate having a circuit is packaged correspondingly to the first substrate on which the MEMS microphone is formed via the first top-layer electrode 234 and the second top-layer electrode 301 .
  • the first top-layer electrode 234 is corresponding to the second top-layer electrode 301 .
  • the MEMS microphone formed in the present invention has a small size.
  • the MEMS microphone and the forming method therefore according to this embodiment has a simple manufacturing and packaging process, a small size, good signal-to-noise ratio performance, and high interference immunity.
  • FIG. 17 is a schematic flowchart of a method for forming a MEMS microphone according to a third embodiment of the present invention, and the method includes the following steps S 301 to S 312 .
  • Step S 301 providing a first substrate having a first surface and a second surface opposite to the first surface.
  • Step S 302 forming, on the first surface of the first substrate, a sensitive diaphragm and a plurality of interconnects.
  • Step S 303 forming a dielectric layer by which the sensitive diaphragm and the plurality of interconnects are covered.
  • Step S 304 forming a plurality of first through holes within the dielectric layer, with the first through holes being corresponding to the interconnect.
  • Step S 305 forming a polycrystalline silicon layer on a surface of the dielectric layer, with the polycrystalline silicon layer filling the first through hole.
  • Step S 306 etching the polycrystalline silicon layer to form a fixed electrode corresponding to the sensitive diaphragm and a top-layer electrode corresponding to the first through hole, with the fixed electrode having a second through hole running through the fixed electrode.
  • Step S 307 providing a second substrate within which a circuit is formed, with the second substrate having a third surface and a fourth surface, and a top-layer electrode being formed on the third surface of the second substrate.
  • Step S 308 forming a bonding layer on a surface of the top-layer electrode to from a second top-layer electrode, with the second top-layer electrode being corresponding to the first top-layer electrode.
  • Step S 309 aligning the second top-layer electrode with the first top-layer electrode, and bonding the second top-layer electrode to the first top-layer electrode via the bonding layer.
  • Step S 310 removing a part of the first substrate from the second surface to form a first opening.
  • Step S 311 removing a part of the second substrate from the fourth surface to form a second opening.
  • Step S 312 removing the dielectric layer corresponding to the first opening from the first opening and/or the second opening, until the first opening becomes in communication with the second opening, so as to form an air cavity.
  • the bonding layer is formed on the top-layer electrode on the second substrate, and the top-layer electrode on the second substrate and the bonding layer located on the top-layer electrode constitute the second top-layer electrode.
  • a first substrate is packaged correspondingly to a second substrate via the second top-layer electrode corresponding to the first top-layer electrode.
  • FIG. 18 is a schematic flowchart of a method for forming a MEMS microphone according to a fourth embodiment of the present invention, and the method includes the following steps S 401 to S 412 .
  • Step S 401 providing a first substrate having a first surface and a second surface opposite to the first surface.
  • Step S 402 forming, on the first surface of the first substrate, a sensitive diaphragm and a plurality of interconnects.
  • Step S 403 forming a dielectric layer by which the sensitive diaphragm and the plurality of interconnects are covered.
  • Step S 404 forming a plurality of first through holes within the dielectric layer, with the first through holes being corresponding to the interconnect.
  • Step S 405 forming a polycrystalline silicon layer on a surface of the dielectric layer, with the polycrystalline silicon filling the first through hole.
  • Step S 406 etching the polycrystalline silicon layer to form a fixed electrode corresponding to the sensitive diaphragm, with the fixed electrode having a second through hole running through the fixed electrode.
  • Step S 407 forming, on the surface of the dielectric layer, a first metal top-layer electrode which corresponding to the first through hole.
  • Step S 408 providing a second substrate within which a circuit is formed, with the second substrate having a third surface and a fourth surface, and a second top-layer electrode being formed on the third surface of the second substrate.
  • Step S 409 aligning the second top-layer electrode with the first top-layer electrode, and bonding the second top-layer electrode to the first top-layer electrode.
  • Step S 410 removing a part of the first substrate from the second surface to form a first opening.
  • Step S 411 removing a part of the second substrate from the fourth surface to form a second opening.
  • Step S 412 removing the dielectric layer corresponding to the first opening from the first opening and/or the second opening, until the first opening becomes in communication with the second opening, so as to form an air cavity.
  • step S 401 to step S 405 reference may be made to step S 201 to step S 205 in the second embodiment.
  • step S 406 reference may be made to step S 206 which is a corresponding step of forming the fixed electrode and the second through hole.
  • step S 407 is carried out, in which a first top-layer electrode made from metal and corresponding to the first through hole is formed.
  • the first top-layer electrode made from metal is not formed in the same deposition process or the same etching process as the fixed electrode. Instead, the first top-layer electrode made from metal and corresponding to the first through hole is formed on the surface of the dielectric layer by an additional physical vapor deposition process.
  • the material of first top-layer electrode made from metal is a conductor, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • Step S 408 is carried out.
  • a second substrate is provided, within which a circuit is formed.
  • the second substrate has a third surface and a fourth surface, and a second top-layer electrode being formed on the third surface of the second substrate.
  • the second substrate may include a semiconductor material.
  • the second substrate may include a single crystal semiconductor material such as single crystal silicon or single crystal silicon-germanium.
  • the circuit (not shown) formed within the second substrate functions to drive the MEMS microphone and process a signal output by the MEMS microphone. That is, when the MEMS microphone receives an acoustic signal, the acoustic signal can be sensed by the sensitive diaphragm 210 , and transmitted to the circuit via the interconnect electrically coupled to the sensitive diaphragm 210 or the fixed electrode 232 , and processed by the circuit.
  • the circuit may be a CMOS circuit.
  • the forming process for the circuit is a standard forming process for a CMOS circuit, which will not be described in detail here.
  • a suitable CMOS circuit can be selected by those skilled in the art depending on the design and parameter of the MEMS microphone. Practically, the circuit may also be other circuits which are formed within the second substrate, drive the MEMS microphone, and process the signal output by the MEMS microphone. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • a second top-layer electrode is formed on the third surface of the second substrate, and the second top-layer electrode is coupled to the CMOS circuit via the conductive plug located within the second substrate. It should also be noted that the second top-layer electrode corresponds to the first top-layer electrode, and is adapted to bond to the first top-layer electrode, so as to bond the first substrate to the second substrate and form an electrical connection structure.
  • the second top-layer electrode may be made from a conductor, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the forming process for the second top-layer electrode is a physical vapor deposition process. Thereby the second top-layer electrode is bonded to the first top-layer electrode, and no additional bonding layer is needed.
  • step S 409 is carried out, in which the second top-layer electrode made from metal is aligned with and bonded to the first top-layer electrode.
  • the second top-layer electrode made from metal and the first top-layer electrode may be made from a conductor, such as aluminum, gold, silicon, germanium, copper, or an alloy of one or more thereof.
  • the second top-layer electrode is aligned with the first top-layer electrode, and an annealing process is carried out, so that the second top-layer electrode is bonded to the first top-layer electrode.
  • step S 410 to step S 412 reference may be made to step S 210 to step S 212 in the first embodiment.
  • the second substrate having a circuit is packaged correspondingly to the first substrate within which the MEMS microphone is formed via the first top-layer electrode 234 and the second top-layer electrode 301 .
  • the first top-layer electrode 234 corresponds to the second top-layer electrode 301 .
  • the MEMS microphone formed in the present invention has a small size.
  • the MEMS microphone and the forming method therefore according to this embodiment has a simple manufacturing and packaging process, a small size, good signal-to-noise ratio performance, and high interference immunity.
  • FIG. 19 is a schematic flowchart of a method for forming a MEMS microphone according to a fifth embodiment of the present invention, and the method includes the following steps S 501 to S 513 .
  • Step S 501 providing a first substrate having a first surface and a second surface opposite to the first surface.
  • Step S 502 forming, on the first surface of the first substrate, a sensitive diaphragm and a plurality of interconnects.
  • Step S 503 forming a dielectric layer by which the sensitive diaphragm and the plurality of interconnects are covered.
  • Step S 504 forming a plurality of first through holes within the dielectric layer, with the first through holes being corresponding to the interconnect.
  • Step S 505 forming a polycrystalline silicon layer on a surface of the dielectric layer, with the polycrystalline silicon layer filling the first through hole.
  • Step S 506 etching the polycrystalline silicon layer to form a fixed electrode corresponding to the sensitive diaphragm and a top-layer electrode corresponding to the first through hole, with the fixed electrode having a second through hole running through the fixed electrode.
  • Step S 507 forming a bonding pad on the surface of the dielectric layer.
  • Step S 508 forming a bonding layer on the surface of the dielectric layer to form a first top-layer electrode.
  • Step S 509 providing a second substrate within which a circuit is formed, with the second substrate having a third surface and a fourth surface, a second top-layer electrode is formed on the third surface of the second substrate, and the second top-layer electrode corresponds to the first top-layer electrode.
  • Step S 510 aligning the second top-layer electrode with the first top-layer electrode, and bonding the second top-layer electrode to the first top-layer electrode via the bonding layer.
  • Step S 511 removing a part of the first substrate from the second surface to form a first opening through which the sensitive diaphragm is exposed.
  • Step S 512 removing a part of the second substrate from the fourth surface to form a second opening corresponding to the first opening and a fourth opening through which the bonding pad is exposed.
  • Step S 513 removing the dielectric layer corresponding to the first opening from the first opening and/or the second opening, until the first opening becomes in communication with the second opening, so as to form an air cavity.
  • step S 501 to step S 506 reference may be made to step S 201 to step 206 and FIG. 5 to FIG. 10 in the second embodiment.
  • a bonding pad 236 is formed on the surface of the dielectric layer 220 .
  • the bonding pad is adapted to provide an electrical connection platform for the MEMS microphone.
  • the bonding pad is generally made from metal, for the reason that the bonding pad 236 has a larger area and need to bear a certain pressure from wire bonding.
  • the forming process for the bonding pad 236 may be such a process in which a metal layer (not shown) is deposited by a physical vapor deposition process, and the metal layer is photoresist patterned and etched to form the bonding pad 236 .
  • the specific step of forming the bonding pad 236 can be determined by those skilled in the art depending on the specific requirement of the MEMS microphone product, and reference may be made to the existing step of forming the bonding pad.
  • step S 508 to step S 511 are carried out, and reference may be made to corresponding step S 207 to step S 210 and FIG. 11 to FIG. 16 in the second embodiment.
  • step S 512 is carried out. Referring to FIG. 21 , a part of the second substrate 300 is removed from the fourth surface IV to form a second opening 310 corresponding to the first opening 240 and a fourth opening 311 through which the bonding pad 236 is exposed.
  • a photoresist pattern is formed on the fourth surface IV, with the photoresist pattern being corresponding to the second opening 310 and the fourth opening 311 ; and the second substrate 300 is etched by using the photoresist pattern as a mask, with the second opening 310 being formed in the same etching process as the fourth opening 311 .
  • the second opening 310 has the same depth as the fourth opening 311 due to a design characteristic of the MEMS microphone in this embodiment, the second opening 310 can be formed in the same etching process as the fourth opening 311 . Thereby some process steps will be eliminated and production cost will be saved.
  • step S 513 by carrying out step S 513 , the dielectric layer 220 corresponding to the first opening 240 is removed from the first opening 240 and/or the second opening 310 , until the first opening 240 becomes in communication with the second opening 310 , so as to form an air cavity 320 .
  • the MEMS microphone formed by the method for forming the MEMS microphone according to the fifth embodiment includes:
  • a first substrate 200 ; a plurality of interconnects 211 formed on the first surface I of the first substrate 200 ; a dielectric layer 220 by which the plurality of interconnects 211 are covered; a conductive plug 223 located within the dielectric layer 220 and electrically coupled to the interconnect 211 ; a first top-layer electrode 234 located on a surface of the dielectric layer 220 and electrically coupled to the conductive plug 223 ; a bonding pad 236 located on the surface of the dielectric layer 220 ; a bonding layer 235 located on a surface of the first top-layer electrode 234 ; a second top-layer electrode 301 located on a surface of the bonding layer 235 and corresponding to the first top-layer electrode 234 ; a second substrate 300 , within which a circuit is formed, located on a surface of the second top-layer electrode 301 ; an air cavity 320 running through the first substrate 200 and the second substrate 300 ; a sensitive diaphragm 210 located within the air cavity
  • the bonding pad 236 formed on the surface of the dielectric layer 220 there is provided with the bonding pad 236 formed on the surface of the dielectric layer 220 , and the bonding pad 236 is exposed through the fourth opening 311 . And no additional step of forming the exposed bonding pad is needed in the subsequent packaging process, thereby some packaging process steps will be eliminated and production cost will be saved.
  • FIG. 23 is a schematic flowchart of a method for forming a MEMS microphone according to a sixth embodiment of the present invention, and the method includes the following steps S 601 to S 611 .
  • Step S 601 providing a first substrate having a first surface and a second surface opposite to the first surface.
  • Step S 602 forming, on the first surface of the first substrate, a sensitive diaphragm and a plurality of interconnects.
  • Step S 603 forming a dielectric layer by which the sensitive diaphragm and the plurality of interconnects are covered.
  • Step S 604 forming a plurality of first through holes within the dielectric layer, with the first through holes being corresponding to the interconnect.
  • Step S 605 forming a polycrystalline silicon layer on a surface of the dielectric layer, with the polycrystalline silicon layer filling the first through hole.
  • Step S 606 etching the polycrystalline silicon layer to form a fixed electrode corresponding to the sensitive diaphragm and a top-layer electrode corresponding to the first through hole, with the fixed electrode having a second through hole running through the fixed electrode.
  • Step S 607 forming a bonding layer on a surface of the top-layer electrode to form a first top-layer electrode.
  • Step S 608 providing a second substrate within which a circuit is formed, with the second substrate having a third surface and a fourth surface, and a second top-layer electrode and a bonding pad being formed on the third surface of the second substrate.
  • Step S 609 aligning the second top-layer electrode with the first top-layer electrode, and bonding the second top-layer electrode to the first top-layer electrode via the bonding layer.
  • Step S 610 removing a part of the second substrate from the fourth surface to form a second opening through which the fixed electrode is exposed.
  • Step S 611 removing a part of the first substrate from the second surface to form a first opening which is in communication with the second opening and a third opening through which the bonding pad is exposed.
  • step S 601 to step S 07 reference may be made to step S 201 to step 207 and FIG. 5 to FIG. 11 in the second embodiment.
  • step S 608 is carried out.
  • a second substrate 300 is provided, within which a circuit (not shown) is formed, with the second substrate 300 having a third surface III and a fourth surface IV, and a second top-layer electrode 301 and a bonding pad 302 being formed on the third surface III of the second substrate 300 .
  • the second substrate 300 may include a semiconductor material.
  • the second substrate 300 may include a single crystal semiconductor material such as single crystal silicon or single crystal silicon-germanium.
  • the circuit (not shown) formed within the second substrate 300 functions to drive the MEMS microphone and process a signal output by the MEMS microphone. That is, when the MEMS microphone receives an acoustic signal, the acoustic signal can be sensed by the sensitive diaphragm 210 and transmitted to the circuit via the interconnect electrically coupled to the sensitive diaphragm 210 or the fixed electrode 232 , and processed by the circuit.
  • the circuit may be a CMOS circuit.
  • the forming process for the circuit is a standard forming process for a CMOS circuit, which will not be described in detail here.
  • a suitable CMOS circuit can be selected by those skilled in the art depending on the design and parameter of the MEMS microphone. Practically, the circuit may also be other circuits which are formed within the second substrate, drive the MEMS microphone, and process the signal output by the MEMS microphone. It should be noted specifically here that the scope of protection of the present invention should not be limited excessively.
  • a second top-layer electrode 301 is formed on the third surface III of the second substrate 300 , which is coupled to the CMOS circuit via the conductive plug located within the second substrate. It should also be noted that the second top-layer electrode corresponds to the first top-layer electrode, and is adapted to bond to the first top-layer electrode, so as to bond the first substrate to the second substrate and form an electrical connection structure.
  • the forming process for the second top-layer electrode 301 is an existing semiconductor process.
  • the specific forming step include: forming a conductive material layer on the third surface III of the second substrate 300 ; and removing a redundant portion of the conductive material layer by lithography process so as to form the second top-layer electrode 301 .
  • a bonding pad of the MEMS microphone is also formed in step S 608 in this embodiment as compared with the second embodiment.
  • the bonding pad 302 is adapted to provide an electrical connection platform for the MEMS microphone.
  • the bonding pad 302 is generally made from metal for the reason that the bonding pad 302 has a larger area and need to bear a certain pressure from wire bonding.
  • the forming process for the bonding pad 302 may be such a process in which a metal layer (not shown) is deposited by physical vapor deposition process, and the metal layer is photoresist patterned and etched to form the bonding pad 302 .
  • the specific step of forming the bonding pad 302 can be determined by those skilled in the art depending on the specific requirement of the MEMS microphone, and reference may be made to the existing step of forming the bonding pad.
  • step S 609 by carrying out step S 609 , the second top-layer electrode 301 is aligned with the first top-layer electrode 234 , and the second top-layer electrode 301 is bonded to the first top-layer electrode 234 via the bonding layer 235 .
  • the bonding layer 235 is made from a conductive bonding material. Specifically, the bonding layer 235 is formed on a surface of the second top-layer electrode 301 or a surface of the first top-layer electrode 234 . And the second top-layer electrode 301 is bonded to the first top-layer electrode 234 .
  • step S 610 by carrying out step S 610 , a part of the second substrate 300 is removed from the fourth surface IV to form a second opening 310 through which the fixed electrode is exposed.
  • a photoresist layer (not shown) on the fourth surface IV is formed; the photoresist layer is exposed and developed so as to form a photoresist pattern corresponding to the second opening 310 within the photoresist layer; the second substrate 300 is etched by using the photoresist pattern as a mask, until the second opening 310 is formed, through which the fixed electrode is exposed.
  • step S 611 by carrying out step S 611 , a part of the first substrate 200 is removed from the second surface II to form a first opening 410 which is in communication with the second opening 310 , and a third opening 411 through which the bonding pad is exposed.
  • a photoresist layer (not shown) on the second surface II is formed; the photoresist layer is exposed and developed so as to form, within the photoresist layer, a photoresist pattern corresponding to the first opening 410 and the third opening 411 ; and the first substrate 200 is etched by using the photoresist pattern as a mask, until the first opening 410 and the third opening 411 are formed, with the second opening 310 being in communication with the first opening 410 , and the bonding pad 302 being exposed through the third opening 411 .
  • the first opening 410 has the same depth as the third opening 411 depending on a design of the MEMS microphone in this embodiment, the first opening 410 can be formed in the same etching process as the third opening 411 . Thereby some process steps will be eliminated and production cost will be saved.
  • the MEMS microphone formed by the method for forming the MEMS microphone according to the sixth embodiment includes:
  • a first substrate 200 a plurality of interconnects 211 formed on the first surface I of the first substrate 200 ; a dielectric layer 220 by which the plurality of interconnects 211 are covered; a conductive plug 223 located within the dielectric layer 220 and electrically coupled to the interconnect 211 ; a first top-layer electrode 234 located on a surface of the dielectric layer 220 and electrically coupled to the conductive plug 223 ; a bonding layer 235 located on a surface of the first top-layer electrode 234 ; a second top-layer electrode 301 located on a surface of the bonding layer 235 and corresponding to the first top-layer electrode 234 ; a bonding pad 302 ; a second substrate 300 , within which a circuit is formed, located on a surface of the second top-layer electrode 301 and the bonding pad 302 ; an air cavity running through the first substrate 200 and the second substrate 300 , with the air cavity being comprised of the first opening 410 and the second opening 310 ;
  • the MEMS microphone formed in the sixth embodiment of the present invention has the bonding pad formed on the surface of the second substrate 300 , and the bonding pad is exposed through the third opening 411 . And no additional step of forming the exposed bonding pad is needed in the subsequent packaging process, thereby some packaging process steps will be eliminated and production cost will be saved.
  • the MEMS microphone formed in the seventh embodiment of the present invention includes: a first substrate 200 ; a plurality of interconnects 211 formed on the first surface I of the first substrate 200 ; a dielectric layer 220 by which the plurality of interconnects 211 are covered; a conductive plug 223 located within the dielectric layer 220 and electrically coupled to the interconnect 211 ; a first top-layer electrode 234 located on a surface of the dielectric layer 220 and electrically coupled to the conductive plug 223 ; a bonding layer 235 located on a surface of the first top-layer electrode 234 ; a second top-layer electrode 301 located on a surface of the bonding layer 235 and corresponding to the first top-layer electrode 234 ; a second substrate 300 , within which a circuit is formed, located on a surface of the second top-layer electrode 301 ; an air cavity 320 running through the first substrate 200 and the second substrate 300 ; a fixed electrode 232 located within the air cavity 320
  • the MEMS microphone formed in the seventh embodiment of the present invention has the same components as the MEMS microphone formed in the second embodiment, except that the positions of the fixed electrode 232 and the sensitive diaphragm 210 are exchanged.
  • the forming method in this embodiment reference may also be made correspondingly to the forming method in the second embodiment.
  • steps of forming the fixed electrode 232 and forming the sensitive diaphragm 210 should be adjusted accordingly.
  • the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment and the sixth embodiment reference may also be made to the MEMS microphone formed in the seventh embodiment.
  • the position of the fixed electrode 232 and the sensitive diaphragm 210 may be adjusted similarly without affecting the scope of the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment and the sixth embodiment.
  • the MEMS microphone formed in the eighth embodiment of the present invention includes: a first substrate 500 ; a plurality of interconnects 511 and a sensitive diaphragm 510 formed on the first surface I of the first substrate 500 ; a dielectric layer 520 by which the plurality of interconnects 511 and a part of the sensitive diaphragm 510 are covered; a conductive plug 523 located within the dielectric layer 520 and electrically coupled to the interconnect 511 ; a first top-layer electrode 534 located on a surface of the dielectric layer 520 and electrically coupled to the conductive plug 523 ; a bonding layer 535 located on a surface of the first top-layer electrode 534 ; a second top-layer electrode 601 located on a surface of the bonding layer 535 and corresponding to the first top-layer electrode 534 ; a second substrate 600 , within which a circuit is formed, located on a surface of the second top-layer electrode 601 ; an air cavity 620
  • the design and the position of the sensitive diaphragm may be adjusted similarly without affecting the scope of the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment, the sixth embodiment and the seventh embodiment.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Manufacturing & Machinery (AREA)
  • Pressure Sensors (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Micromachines (AREA)
US14/004,822 2011-03-15 2012-02-22 MEMS microphone and forming method therefor Active 2032-03-25 US9674619B2 (en)

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CN201110061561 2011-03-15
PCT/CN2012/071441 WO2012122871A1 (zh) 2011-03-15 2012-02-22 Mems麦克风结构及其形成方法

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